The present invention relates generally to an optical sensor apparatus and method for remotely monitoring a utility meter or the like and transmitting the readout therefrom to a central location. More particularly, the present invention relates to an optical sensor apparatus and method for remotely monitoring a utility meter or the like by use of an optically sensitive, dynamic RAM (random-access read/write memory) device.
Electric, gas, water or other meters are typically characterized by a plurality of rotatable gears or shafts which are so interrelated that each successive shaft is angularly diplaced on a 10 to 1 basis with respect to its neighbor, whereby a direct decimal readout of the meter is enabled by means of indicator pointers which rotate with the several shafts about dials on a faceplate. In a typical power utility installation, for example, periodic reading of the meter is conducted by an individual who inspects the readings at each of the plurality of dials associated with the several shafts of the multistage meter, and thereby may record a direct decimal value.
Within recent years a considerable amount of interest has been generated in automating the readout function of the multistage or "polydecade" meter, as generally described above. Among the reasons that may be cited for such interest is a desire to reduce the cost of manual servicing, and the fact that the meters sought to be read are often in relatively inaccessible places in homes, in factories and in other installations. Moreover, interest is largely centered in providing an automated readout in such a form that said readout may be directly transmitted as, for example, by conventional transmission lines to the utility company or other provider of the services recorded on the meter. Such a result would not only vastly increase the efficiency and speed with which the meter readout process may be available to suppliers, but moreover provides as desired a virtually continuous capability for obtaining such information.
There has been considerable effort expended in providing means and apparatus for reading meters at a distance, for example, through telephone lines and the like. Most of such previous meter readings have required that some internal mechanical or electrical alteration be made to the meter itself, and considerable time and expense is required in putting the altered meter into use. In addition, when such alteration is performed there is the possibility of voiding the meter manufacturer's warranty. Many previous meter reading devices utilize sliding electrical contacts which has prevented their use in explosive atmospheres. Furthermore, in many such metering devices, changes in the output signal have been noted due to the aging of the components which can change the mechanical and or electrical characteristics.
Other meter reading devices have used photoelectric cells, so that no mechanical connection is needed between the meter and the meter readout. However, these reading devices have not been satisfactory because a reliable source of light must be provided and the face of the photoelectric cell must be kept sufficiently clean so that the light impinging on the photoelectric cell will not be diminished sufficiently to give a false reading.
Furthermore, the data from these systems and many other systems is extremely volatile as they monitor the disk or rotor movement of the meter. Accordingly, any slight disruption or interruption in the monitoring process will result in a complete data loss requiring that the meter be inspected manually to obtain a new start-up reading.
As disclosed in U.S. Pat. No. 3,852,726, a magnetic pointer in cooperation with read switches is utilized to provide a digital signal representative of the analog-type meter reading. In addition to other problems, this patent does not provide for resolution of ambiguities that might result from positioning of the pointer directly between two read switches. Also, this patent only provides for a readout at the remote site.
The present invention solves these and many other problems associated with many remote meter monitoring devices.